Fix DatagramChannelMulticastTest#test_multicastLoopOption_IPv6

DatagramChannelMulticastTest#test_multicastLoopOption_IPv6 was failed
because any SocketAddress can't be received from DatagramChannel.
The defect comes from that network interface for send is unspecified
to the DatagramChannel while sending multicast datagrams.
We should apply the modification of
"Fix DatagramChannelMulticastTest#test_joinAnySource_IPv6" here as well.

Bug: 63515474
Test: libcore.java.nio.channels.DatagramChannelMulticastTest
Test: Confirmed that on some devices, the following test
      fails before this CL:
libcore.java.nio.channels.DatagramChannelMulticastTest#test_multicastLoopOption_IPv6

Change-Id: I81f37412d12b0f7f07efd80a26639a658775c950